As an industrial fabric with a concave-convex surface, fabrics woven with warps and wefts have so far been used widely. Such fabrics have been used in a variety of fields including wires for manufacture of non-woven fabrics, papermaking wires, and conveyor belts. Their concave-convex structure is effective for imparting marks or special feeling to paper or non-woven fabrics or for preventing slippage of transported goods.
In particular, fabrics for putting marks to non-woven fabrics or paper are strictly requested to satisfy fiber supporting property, sheet release property and adaptability to high-speed machine as well as adequate height of their concaves and convexes. In recent years, with a speedup of non-woven fabric manufacturing machine or paper manufacturing machine, the above-described request has been stricter.
Fabrics for putting marks can be manufactured by various processes. As described in Japanese Patent Laid-Open Publication No. 2005-9013, such a fabric is manufactured by forming a float (long crimp) of warps and wefts on the fabric surface, thereby providing a height difference in each region. In Japanese Patent Laid-Open Publication No. 2004-27407, described is a process of arranging warps of a large diameter at some intervals, and putting marks by utilizing a difference in height at the top portion of a knuckle between a warp of a small diameter and a warp of a large diameter. These processes are effective for giving a geometric pattern, characters or strains, or sporadic patterns different from main pattern, but are not suited for giving bulkiness to non-woven fabrics by making use of the constitution of the whole fabric.
At present, fabrics for putting marks have problems such as scattering of a sheet raw material owing to the speedup of machine. In wet forming, fibers are supplied to the machine together with a large amount of water so that the speedup of machine can be actualized to some extent. In dry forming, however, fiber raw materials very light in weight are supplied onto a fabric so that they sometimes scatter when treated by a high-speed machine. This phenomenon is marked when fiber raw materials are supplied onto a fabric having a relatively flat surface. A fabric having a structure facilitating entanglement of fibers or having a marked concave-convex structure will overcome the problem of scattering. But in such a fabric, fibers sometimes get under constituent yarns to deteriorate the sheet release property. As described above, a property for preventing fibers from scattering, sheet release property and concave-convex imparting property are properties which cannot be satisfied simultaneously.